MIAMI, Fla. – While the debate grows on how to tackle global jihadism on the Internet, some security experts warn that "cyber vigilantes" — people who track and help shut down terror-related Web sites — are compromising government investigations with their amateur sleuthing tactics.

Michael Radu, a senior fellow at the Foreign Policy Research Institute and an expert on terror-related Web sites, said the government is already overburdened trying to monitor the thousands of sites on the Web believed to contain radical Muslim messages. These cyber vigilantes, he said, are not helping.

“It is very unlikely they will find something of significance in the Internet that the government doesn’t already know," Radu said. "They are redundant at best.”

One of them is Bill Warner, a Sarasota, Fla.-based private investigator and a self-proclaimed cyber-crusader.

Just last month alone, Warner was instrumental in helping shut down three Web sites hosted by a Tampa Internet service provider (ISP) that contained text, images and video related to attacks on U.S. troops in Iraq and Afghanistan.

One site contained footage of a U.S. military mine sweeper being blown up by an Improvised Explosive Device (IED). According to Warner, the site claims that all the troops aboard the vehicle were killed. (www.alekhlaas.info)

The same site, which is still operational, shows what appears to be footage of fighters in Afghanistan firing on U.S. troops and what is believed to be the destruction of an American mine sweeper in Iraq.

Warner said the popular site is nearing 19 million hits over the last 10 months, and is among a growing number meant to incite would-be followers to join the ranks of extremist groups like Al Qaeda and provide information on how to carry out attacks and build weapons.

"This is what Al Qaeda does now," said Warner.

He said the World Wide Web is where the real fight for global jihad is being fought.

Sites such as these are often hosted by ISPs in the U.S. because they have large bandwidth, making posting and viewing large videos easier. Because of the anonymous nature of the Internet and foreign language content, U.S.-based ISPs can't provide sufficient screening and oversight.

Warner said he alerted the local police and the FBI in Tampa after he identified three Web sites hosted by the Florida ISP. In some cases the sites were removed within hours. But he said others remained online for days after he reported their presence.

But not everyone thinks Warner's vigilance is helpful.

"There are a lot of weekend warriors and quasi vigilantes out there that think they can do what the government can't," said a private intelligence contractor for the U.S. government who has been investigating jihadist Web sites for more than 15 years. The contractor spoke to FOXNews.com on condition of anonymity due to his continuing work with U.S. intelligence.

He said that when cyber-sleuths alert authorities or ISPs to the whereabouts of an extremist site, the page is removed — only to reappear somewhere else, and sometimes within hours.

"For those working in the intelligence community, it becomes extremely costly, because then they have to go looking for the sites all over again," said the private intelligence contractor, noting that U.S. intelligence often knows of the sites for a long time and monitors their traffic to look for clues to their origins, creators and visitors.

When the site comes down, he said, intelligence investigations can be ruined.

"They have good intentions, but end up doing more harm than good," he said.

But Yigal Carmon, President of the Middle East Media Research Institute, a Middle East media monitoring group, said the sites reported by Warner are tools of "ideological recruitment" that should be removed from the Internet entirely, and especially from American ISPs.

"Why is it that [an] American ISP can host them?" Carmon asked. "When these sites appear there, the whole war on terrorism becomes a joke."

Lt. Col. Joseph Felter of West Point’s Combating Terrorism Center said the increased participation to battle online terrorists is a good thing.

"The more people that we get involved combating the threat, the better,” said Felter. “God knows the enemies are getting a whole lot of people on board.”

But Radu warns that without specific knowledge of extremist groups or languages like Arabic, Urdu and Farsi, Cyber vigilantes don't always understand what they're looking at.

“Those people are nuisances, nuisances that already burden an overworked government and should be discouraged,” Radu said. “No matter what their intentions are, they are overburdening the government” and “have nothing to contribute.”

Cyber vigilante Aaron Wiseburd has taken a similar approach to Warner, tackling terror-related Web sites and reporting his findings to authorities.

Wiseburd, the creator of the Web monitoring site Internet Haganah, which collects and stores intelligence for governments to use, said he was responsible for the dismantling of thousands of extremist sites.

Weisburd's critics say posting of sensitive material on his site may reveal too much and jeopardize ongoing investigations.

Wiseburd is reticent to discuss his efforts, due to safety concerns — he said he has received death threats and a handwritten note mailed to his home from a disgruntled site creator. But he said he won't stop fighting the emerging threat of cyber terrorism.

He and Warner say their work is an important part of stopping terrorist groups from gaining a recruiting foothold in the U.S. and inspiring others to form their own spin-off extremist groups.

"If a Web site is calling for U.S. citizens to be killed, it should be shut down," Warner said. "If it incites these wackos who don't have direct allegiance to Al Qaeda to commit attacks, then it shouldn't be on the Internet, period."

But a private intelligence contractor said winning the War on Terror isn't just about shutting down sites; it's about tackling the heart of the problem.

"Great. Somebody shut down a bunch of websites. What we're trying to do is find out where the terrorists are."